Wish to visit Great Wall from Tianjin. Appreciate if you please advise which part will be suitable?

Since you will leave from Beijing, I'd recommend you visit the most famous section - Badaling. You can take a bullet train from Tianjin to Beijing South. Then take local subway line 4 to Xizhimen, from which you can easily walk to the North Railway Station. Take a S2 train there to reach Badaling directly. Although another good section named Huangyaguan is in Tianjin, it is far from the downtown. You may give it up for the limited time.